This invention relates generally to anchor devices designed for use in tying down large objects such as equipment or mobile homes, and, in particular, to a unique bolt for use in such devices. Typical examples of anchor devices of the aforesaid type are disclosed in U.S. Pat. Nos. 3,416,763, 3,638,912, and 3,825,227.
These anchor devices generally include a shank member formed with helical blades or similar holding structures that permit the shank member to be, in effect, either screwed into the ground and held thereat or otherwise secured in place, and the shank member includes a top portion having spaced side walls with aligned openings formed therein to receive one or more rotatable bolts having slots or other means for receiving and holding a strap, wire or the like which is passed over the object to be tied down and attached to the bolt of the anchor device. It is common practice, as shown for example in the aforesaid U.S. Pat. No. 3,416,763, to form at least one of the aforesaid aligned openings with a square or flat-sided configuration, and use a bolt having a head formed with a configuration that corresponds to that of the flat-sided opening so that the bolt can be moved to a first disposition at which the head portion thereof is spaced from the opening to permit rotation of the bolt to tighten the strap, and, when the strap is tightened, so that the bolt can be moved to a second disposition at which the head position thereof is located within the opening to prevent further rotation of the bolt, whereby the strap is maintained in tension across the object being tied down.
In these conventional anchor devices, the head of the bolt has flat sides that extend longitudinally in parallel relation to the axis of the bolt so that the cross-sectional area of the head is constant along such longitudinal extent, and while this construction permits the bolt head to fit into the correspondingly shaped opening at any point along the longitudinal extent of the bolt head, such construction also has certain disadvantages. Because the bolt head passes into and is received within the opening, it must be slightly smaller than the opening to permit the user of the anchor to be able to place the bolt head into the opening with relative ease. This dimensional difference, combined with normal manufacturing tolerances inherent in such devices, necessarily results in a somewhat loose fit between the bolt head and opening when the former is received by the latter, and this loose fit creates a situation in which the bolt head is free to move rotationally to a small degree with respect to the larger opening. When it is recognized that the flat faces of the bolt head intersect one another along an edge that is generally straight or slightly rounded which, in effect, forms a point at each such intersection, it will be appreciated that the aforesaid rotational movement of the bolt head within the opening will create a situation in which the corners of the bolt head come into essentially point contact with the flat sides that form the opening. In applications of anchor bolts to hold down large objects, such as mobile homes, a substantial rotational force is imposed on the bolt when the straps held thereby are in a state of tension, and this force, combined with the aforesaid point contact between the bolt head and the flat sides of the opening, generates substantially stress that can result in premature failure of the anchor. Moreover, this stress will, in time, result in the corners of the bolt head being flattened, whereby the dimensional differences between the bolt head and the openings is further increased.
Additionally, conventional anchor bolts have, heretofore, always been formed of solid metal which makes them somewhat expensive to produce, and which results in relatively high shipping costs because of the weight of the solid bolt. Also, since the head of the bolt is solid, only one size tool or wrench can be used to engage the bolt head for turning the bolt to tension the strap as described above.
In accordance with the present invention, an anchor bolt is provided which overcomes the above-described operational drawbacks of conventional anchor bolts, which reducing the expenses associated with the manufacturing and shipping of such bolts.